The invention relates in general to a garage door operator and, in particular, to a garage door operator having an optical or infrared obstacle sensing system adapted to generate an infrared or optical light beam across a door opening to detect the presence of obstacles to signal other portions of a garage door operator when obstacles are present to prevent a garage door from being closed on the obstacle or to cause the door to reverse and open away from the obstacle.
One of the problems associated with typical garage door operators is that when a garage door operator is commanded to close, the door operator may close onto an obstacle in the way of the door causing damage to the operator. The door operator also may close on an object which may be damaged such as a automobile, child's tricycle or even upon a person. As a result, a number of schemes have been adopted to prevent the power operated garage doors from closing on obstacles.
A number of garage door operators include edge-type sensors usually comprising a flexible strip attached to a bottom edge of the garage door, which flexible strip deforms when it comes in contact with an obstacle. Deformation of the flexible strip may increase pressure of a trapped fluid within the strip or close switches signaling the garage door operator that an obstacle has been encountered. The garage door operator then switches into its up mode and immediately raises the garage door. Such systems, however, are relatively expensive to install as the strip must be attached to the bottom of the garage door, it must be aligned and the material cost is relatively high.
Other systems, such as the Chamberlain Protector optical detection system employ an optical detector having an infrared radiation unit positioned on one side of a garage door opening and an infrared receiving unit positioned on the other side of the garage door opening. Such units are somewhat more expensive as they require separate emitter and radiator heads and require good alignment between the emitter and the radiator. However, they are attractive from the standpoint of the manufacture of the garage door operator because attenuation of the infrared beam due to the emitter becoming soiled or due to other environmental changes has less effect upon the output of the detector than would occur in a retro-reflector system which requires the beam to travel twice as far, thus attenuating the beam by four times as much under the inverse square law.
What is needed, then is a retro-reflective infrared or optical detection system which can sense when a failure has occurred in the detection system and signal other portions of a garage door operator to open.